Can overnight ups letters come a day or two late?

• shipment tracking software
• late payment charges

Hello I am expecting a large envelope from ups and the lady

sent it to me on wedsday 11/13/2013 and she said it would be here the next day

which is today Thursday 11/14/2013 and I still did not get it is it possible to be

a day or two late its coming form Maryland to Pittsburgh pa

Thanks

Can overnight ups letters come a day or two late?